For someone chasing an ideal of greater beauty and sex appeal, it was a sad death in a foreign hospital, thousands of miles from home. But such was the price paid by 20-year-old Claudia Aderotimi, who travelled from her home in London to America, apparently in a quest for backstreet cosmetic surgery to give herself fuller buttocks.

It was a journey that took her to room 425 of a suburban Hampton Inn hotel near the airport in Philadelphia, where a pair of suspected illegal "surgeons" arranged for her and a friend to be injected with what police believe was silicone. One woman survived the clandestine operation. Aderotimi did not.

Sources close to the investigation say that some time on Monday, about 12 hours after the operation was carried out in a hotel room specially booked for the task, Aderotimi began to complain of severe chest pains and medics were called. She was taken to the nearby Mercy Fitzgerald hospital, where she died in the early hours of Tuesday.

Friends and family are grieving at the family home in Hackney, north London. The woman's sister, Vivian, said: "We found out yesterday. We're still in shock. We need to think about what we have to do. I really don't want to say anything at the moment."

Aderotimi is understood to have paid about $2,000 (£1,200) for the operation. The women who carried out the operation fled and are now the subject of a police manhunt.

"What they were doing at this point does not look legal," said Lieutenant Ray Evers of Philadelphia police. He added that one of the missing women had been identified, and a property in New Jersey had been searched. Her alleged accomplice remains unknown. "No arrests have yet been made," Evers said.

The two so-called surgeons apparently operated together as a team, with one of them acting as the "booker" who arranged the procedure over the internet with clients. The second member of the US-based team was the "injector", who carried out the operation where silicone is injected into the buttocks to give them a fuller appearance.

Aderotimi had travelled to the US with three companions from Britain. She had had the procedure before, in November last year.

Douglas McGeorge, past president of the British Association of Aesthetic Plastic Surgeons, said: "There was a craze for the [Jennifer Lopez] look for a while, where women wanted more voluptuous buttocks and a bit more of a curve, but it's still very much a minority procedure."

It is possible to get buttock implants legally or use complex protein injections to achieve the desired look, but they are expensive and time-consuming and can be difficult to arrange. As a result, an illegal and unregulated cottage-industry has sprung up around cheaper silicone injections for those wishing to indulge in cheap medical tourism. The silicone substance in most of these secretive operations is used as a permanent filler in the body, but is not medically approved in the US for the operation and is banned in some countries.

"The internet is a wonderful tool, but it's open to abuse ... people are often seduced by less credible options because they are cheaper. It can't have cost very much money to have the procedure done in a hotel room," McGeorge said.

US federal health officials have had reports of scores of injuries due to the operations in recent years. Silicone is highly dangerous if it gets into the bloodstream and can cause death if it reaches the heart or lungs.

The US Food and Drug Administration warns silicone injections can cause auto-immune problems, physical disfigurement, kidney difficulties as well as fatal blood clots or embolisms.

A full postmortem toxicology report on Aderotimi will not be released for several weeks, but investigators are assuming the silicone got into her vascular system, eventually causing her death.

Last year in New Jersey, a professional model was criminally charged for asking for between $600 and $1,000 for silicone injections. Six of her customers were later sent to hospital with serious infections. In Florida, two women were hospitalised with serious injuries after similar operations went wrong.

In New York city earlier this year, a woman was charged after police discovered she was running an underground injection clinic from her two-bedroom Bronx apartment. Whalesca Castillo got her supplies sent to America from the Dominican Republic.

When investigators searched through her bins, they found more than 100 bottles with silicone residue on them, as well as a bottle of Krazy Glue which amateur practitioners sometimes use to seal surgical wounds.

The most famous victim of the quest for better buttocks was former Miss Argentina Solange Magnano. The 38-year-old married mother of two died in Buenos Aires after a legal operation believed to have involved buttock implants as well as injections.

Her friend, the fashion designer Roberto Piazza, said: "A woman who had everything lost her life to have a slightly firmer behind."